The present invention relates to a method for manufacturing fused quartz glass from a vaporizable silicon compound or, more particularly, to a method for manufacturing fused quartz glass containing a controlled amount of hydroxy groups.
As is well known, the traditional method for the manufacture of fused quartz glass is melting of quartz powder in a oxyhydrogen flame and shaping the molten quartz into desired forms. This method is, however, susceptible to the unavoidable intermixing of various impurities into the fused quartz glass so that, in accordance with the recent demand for fused quartz glass of higher and higher purity, a synthetic method has come into practice in which a halide of silicon such as silicon tetrachloride is subjected to hydrolysis or oxidation to form silicon dioxide and the melt of the thus formed silicon dioxide is deposited on a refractory substrate into a mass of fused quartz glass.
Owing to the excellent optical and chemical properties of fused quartz glass, on the other hand, the fields of application of fused quartz glass have been greatly expanded in recent years including the rapidly developing technology of electronics which requires particularly high purity and uniformity of the fused quartz glass used therein.
The most important matter in respect of the uniformity of the fused quartz glass is the amount of hydroxy groups contained therein. For example, the hydroxy content should be as little as possible in a fused quartz glass to be fabricated into optical fibers since the hydroxy content in the quartz glass is responsible to the increase of the transmission loss of the light through the optical fibers. On the other hand, the hydroxy groups in a quartz glass is effective to increase the resistance of the quartz glass against ionizing radiation so that the material of fused quartz glass to be used in a high intensity radiation field should desirably contain a considerable amount of hydroxy groups as in the window around an atomic reactor. In this connection, it is advantageous to develop a method for manufacturing fused quartz glass according to which the quartz glass product contains hydroxy groups in an amount controlled as exactly as desired while conventional methods are unsatisfactory in respect of the poor reproducibility of the hydroxy content in the fused quartz glass manufactured thereby.